Solar Thermodynamic Panels: Independent Test Challenge

Heat meter for the testing of low carbon heating systemsHeat meter on an air source heat pump system at our training centre

UPDATE: We now have a system being tested in our Thermal Testing Laboratory. More information can be found in the links below.

Solar Thermodynamic Panels

There has been a great deal of talk in the energy industry over the past year on solar thermodynamic panels. Some marketing material and testimonials suggest very promising results, however it seems there is has been no independent testing or verification of these systems in the UK.

As an independent test centre, associated with the National Renewable Energy Centre, we are offering free testing for a solar thermodynamic manufacturer who will supply and install a system for free at our headquarters in Northumberland

Solar collector technology

Marketing literature often compares thermodynamic panels with conventional solar thermal systems, but there are key differences in collector design.

Solar thermal collectors have evolved over the last 30 or so years into mainstream construction products with EN and BS standards. Collectors are usually glazed and combine selective coatings and high insulation levels to maximise the flow temperature and optimise solar energy collection efficiency. In the temperature band for heating water (e.g. 20-50 K above ambient) test results show efficiency is typically 55 to 65% for glazed collectors. Unglazed collectors are rarely, if ever, used for heating domestic hot water in the UK because the efficiency falls quite dramatically with increasing temperature difference; although they are very effective for low temperature applications such as heating swimming pools in summer.

The technology is well proven and typically saves between 50 and 70% of water heating energy; a 4m2 system will typically deliver around 1600 kWh of heat at the tank, using about 45kWh of electricity in the process. Back up heat is usually provided by gas boiler.

Thermodynamic panels are usually unglazed flat plates and use refrigeration technology to boost the flow temperature to the heat the water. It can be thought of as air source heat pump (without the fan) that can take additional gains by collecting solar energy if it is suitably orientated. Thermodynamic panels have the advantage they can produce heat from non-optimal collector orientations, or even at night, because of the temperature uplift the heat pump compression cycle offers. The key question is, how efficient is this process and what carbon saving benefit is there over the existing water heating system bearing in mind the current UK grid electricity carbon content?

COP (coefficient of performance)

Thermodynamic systems use electricity for the heat pump compressor and circulation pump. Therefore, like any other type of heat pump, they will have a COP (coefficient of performance), which is a comparison of the energy taken to run, against the output heat energy from the system.

The COP of air-source heat pumps typically lies in the range of 2 to 4, depending on the weather conditions and season. Lower values are usually associated with domestic hot water production because of the high temperature uplift required; the higher values for spring/autumn space heating. Many heat pump suppliers recommend a hot water set point of 48 to 50°C to improve performance, with a regular pasteurisation cycle to safeguard against legionella (often using an immersion heater to 60°C once a week or fortnight).

EN standard heat pump testing requires COP testing at several temperature conditions and when interpreting these results it is important to compare the same conditions; e.g. A7W35 means water temperature of 35° and ambient of 7°C, for which one manufacturer quotes a COP of 4.13, falling to 2.80 at A-3/35 when the ambient is -3°C. This shows the COPs that can be achieved with a suitably designed low temperature heating system, such as underfloor in-slab. However, heating domestic hot water to 50°C requires a much higher temperature gradient, so it is reasonable to assume the COP will fall.

Some Thermodynamic suppliers suggests the COP lies in the range of 2 to 7 – the question is for UK water heating which end of the range is most realistic?


Thermodynamic panels have been temporarily suspended from the MCS installation database. This doesn’t mean the systems cannot be installed in the UK, but that they will not qualify for any financial incentives etc. which are for MCS approved technologies only.

The reasons given by Gemserv, who run the MCS scheme are:

  • The performance of the products being installed in the UK cannot be fully determined; this is mainly due to the fact that these solar systems are being installed using refrigerant but the 12975 testing and certification through Solar Keymark did not use refrigerant as the heat transfer medium.
  • Systems with a compression heat exchange unit are unable to meet the requirements for completing the SAP and performance estimation calculations required under MCS, for example hybrid type systems are not covered fully within the SAP methodology which is required to be completed under MCS.
  • It is not clear how compliance with Part G of the building regulations is fully met, due to the system’s packaged control strategy. Installers are required to meet all parts of the building regulations under MCS, and it is uncertain if installers are able to do this with the system’s packaged control strategy.
  • It needs to be determined if the classification of these systems within MCS are actually Solar Thermal systems or if they should be classified as Heat Pump systems.

Independent test offer

We are willing to carry out an independent test on a single thermodynamic panel system, if provided with one fully installed with all required fittings at our test facility in Northumberland, free of charge by a manufacturer. Due to current high levels of work, we should be able to start the test after the end of May.

We are an organisation completely independent of manufacturers, and part of the National Renewable Energy Centre group of companies, so will give completely honest and realistic results. Whatever the results, positive or negative, we will release them on our website and to our press contacts. Let’s find out how it compares.

If you feel up to this challenge, please get in touch on

Renewable Energy Training Q2 2013 Calendar Published

We have launched the training schedule for our range of bespoke and accredited renewable energy training courses for April, May and June 2013. This includes our two new, highly popular courses.

New Courses for 2013

G59/2 Connecting Large Scale Embedded Generators: This course is aimed at renewable installers, to give them an understanding of the requirements for connecting large scale renewable generators, and the reasons why these exist. We have received extremely good reviews from the first attendees on these courses. From our first four runs of the course, which trained a total of 20 individuals, we found 94% of attendees found the course useful, which 28% strongly agreeing.

Biomass Awareness : The biomass course is aimed at an introductory level, covering a wide range of issues for domestic and commercial scale biomass heating. This includes case studies, details on the fuel sources, and the building regulations. The Renewable Heat Incentive with regard to biomass is also discussed

Financial Incentives

We are running seminars on both the Green Deal and Renewable Heat Incentive, which provide updates with all the latest changes to these two schemes.

LOGIC Accredited Installer Training

We continue to offer LOGIC accredited installer training for photovoltaic, solar thermal and heat pump systems. These courses are essential for installers to fulfill their MCS requirements.


If your company is a North East England based SME, you could receive 100% funding for course attendance. If you are interested in this, please contact Andrew Tipping at

More Information

The renewable energy training schedule can be downloaded here: Decerna Training Course and Seminar Dates 2013 – apr may jun

Or courses can be booked online here: Renewable Energy Training Calendar

The full prospectus can be downloaded from: Decerna Training Seminar and Workshop prospectus 2013

If you wish to go on a course which is not scheduled in the calendar, please contact us on, we can also carry out our training courses on customer’s premises where possible.